Someone just asked me about receiving an error like this one:
You don't have permission to access "http://www.gap.com/" on this server.
Reference #18.c6a50517.1514639126.176b29aThere are several garbage articles out there talking about this without any indication of what is actually generating this error message.
This Microsoft TechNet post reveals the answer: it comes from the Akamai CDN, a content delivery network used by large sites to speed them up.
Akamai has a helpdesk article about this, including a link to their Client Reputation lookup tool.
Microsoft, which apparently also uses Akamai, has a post of their own about it, noting:
This issue occurs because of the measures that Akamai has implemented to protect its websites from denial-of-service attacks. If a single origin or source tries to connect too frequently, these measures automatically block any IP addresses from that origin or source.
The blockage is usually temporary. As soon as the connection volume remains below the defined thresholds for a while, the block on the affected TCP/IP address is expected to be removed.
From the posts I've seen, it is perhaps a touch too sensitive and sometimes blocks legitimate users. (Perhaps triggered by rapidly opening multiple links in tabs, or multiple people in the same household browsing concurrently?) The fix is to simply wait a bit and try again, though.